A significant and ongoing cause of vehicle damage and risk to life and limb on our nation's roadways is animal-vehicle crashes. Of particular concern are animal-vehicle crashes involving large animals, such as deer, which occur at highway speeds. Typically, such crashes result from the deer or other large animal wandering or dashing in a panic onto a roadway in front of an oncoming vehicle. At highway speeds, the speed of the vehicle makes it almost impossible for the driver to avoid a crash in many cases. This is particularly true since many animals, such as deer, are most active in the low light conditions of dawn and dusk, times at which visibility is reduced and, therefore, available driver reaction time is reduced even further. Costly and dangerous animal-vehicle crashes can occur, however, at any time of day and even at less than full highway speeds.
Many and various attempts have been made to reduce the incidence of animal-vehicle crashes by mounting devices on a vehicle in an attempt to warn or scare animals away from the path of the oncoming vehicle. Many such vehicle mounted devices emit ultrasonic sound waves. A common device of this type is the deer whistle. This purely mechanical device is mounted on a vehicle so that wind passing through the whistle at highway speeds causes the emission of sounds in an ultrasonic frequency range. These devices have proved to be relatively popular, because they are inexpensive. Other systems have employed electronic circuitry to drive one or more speakers to emit ultrasonic sound waves in a variety of different sound patterns. A great advantage of such systems is that the sound emitted is inaudible to humans and, therefore, there is little concern that the driver or passengers or others in the area of the vehicle will be disturbed by the sound produced by such a system. The great disadvantage of devices that produce sounds in an ultrasonic frequency range is that they are ineffective for the prevention of animal-vehicle crashes. In particular, research on animal audio-perception has indicated that white-tail deer hear in the same general range as humans. Therefore, devices that produce sounds in an ultrasonic frequency range will have no affect on preventing deer from wandering or running into an oncoming vehicle either at the front or the side of the vehicle, since the ultrasonic sounds produced by such devices cannot be heard by deer.
Realizing the ineffectiveness of warning systems that have attempted to use ultrasonic sound to scare off deer to reduce the possibility of an animal-vehicle collision, the Total Alert Driver Safety System described in U.S. Pat. No. 5,515,026 to Roger Ewert includes a unit mounted in a car or other vehicle that produces natural sounds in the audible frequency range of 1–20 kHz. The described system employs natural sounds, e.g., clicks, snaps, cracks, pops, crunches, ticks, claps, zaps, etc., in the suggested frequency range that are generated by an electronic sound generator and produced by a speaker mounted on the vehicle. The natural sounds could be recorded, isolated, filtered, digitized, and stored in memory, or a mathematical function which nearly simulates a particular sound could be used to generate the sound wave form. The natural sounds generated by such a system have been found not to induce panic in deer, but rather to induce a natural avoidance instinct, causing the deer to stand alert or wander away from vehicles employing such a system. This system employed switches that might be configured to produce variable sound patterns and intervals which periodically might be reprogrammed to prevent deer and other animals from growing accustomed or “immune” to the alerting signal. The system also received input from a transducer mounted to the vehicle drive train, or from a car's electronic speed sensor or vehicle computer, to determine vehicle speed. Transmission of the animal alerting sound by the system might be initiated manually (e.g., using a foot switch provided in the vehicle) or automatically when the vehicle exceeded a particular speed (e.g., 35 miles per hour). The volume of the sound emitted by the system might be increased as the vehicle velocity increased. Thus, the audible sound emitted by the system preferably was activated, and the volume increased, only at relatively high speeds at which deer-vehicle crashes were most likely to occur, where increased volume was required and, since such high speed travel is unlikely to occur in typical residential or commercial areas, away from areas in which the audible sound might be heard by residents and pedestrians. In addition to sound generation, the system described in U.S. Pat. No. 5,515,026, as well as other systems in the prior art, suggests also the use of flickering lights, e.g., flickering the vehicle headlights momentarily and repeatedly, to create a flickering affect, to reduce the likelihood that an animal will fixate on the oncoming lights of the vehicle and to facilitate the animal's natural avoidance response to the broadcast sound. A separate strobe light might be provided and controlled to flicker in synch with the sounds from the system's speaker.
Although the system described in U.S. Pat. No. 5,515,026 was found to be more effective than systems that generate ultrasonic sounds to alert deer and other large animals to an oncoming vehicle, further improvements are possible. What is desired, therefore, is an improved vehicle mounted animal alerting device that generates sound patterns that are better adapted to induce an alertness response in deer or other large animals, thereby to reduce the chances that such animals will wander or run into the path of an oncoming vehicle in which such a system is mounted. The system preferably automatically adjusts parameters of the audible sound produced thereby in response to vehicle operating conditions. This optimizes the effectiveness of the sounds produced by the system to stimulate the alertness response of animals in the area of the vehicle under vehicle operating conditions for which an animal-vehicle crash is most likely to occur.